SUSCEPTIBILITY T O I N V ITRO T OLERANCE I NDUCTION OF A DULT B CELLS F ROM MICE W ITH A N X -LINKED B -CELL D EFECT*

CBA/N mice, a mutant subline of the CBA/Ca strain, have an X-linked B lymphocyte-immun e defect. These mice and F1 male progeny derived from CBA/N females fail to produce specific antibody after immunization with certain thymicindependent (TI) antigens (1-4). In addition, these mice fail to produce IgM or IgG responses to either the TI or T-dependent derivatives of the hapten phosphorylcholin e (PC) (5, 6). Moreover, analysis of surface membrane characteristics indicates that B cells derived from immune defective mice fail to express determinants that are present on a population of B lymphocytes that appears late in ontogeny. These include minor lymphocyte-stimu lating determinants (7), Lyb5 (8), and Lyb3 (9). Furthermore, the B cells of CBA/N mice have unusually high amounts of surface IgM (sIgM) and exhibit a low ratio of surface 8:/~ heavy chains when compared with the B cells of normal mice (10, 11). These surface characteristics are similar to those that are exhibited by neonatal B cells (10). Taken together, these findings are consistent with the hypothesis that the immune defect(s) in CBA/N mice arise from a maturational arrest either in the development of CBA/N B cells or of a subpopulation of these B